1. Field of the Invention
This invention relates generally to plastic containers that are fabricated from polyethylene terephthalate, which is commonly known by the acronym PET. More specifically, the invention relates to PET containers that are fabricated using an extrusion blow molding process.
2. Description of the Related Technology
Many products that were previously packaged using glass containers are now being supplied in plastic containers, such as containers that are fabricated from polyesters such as polyethylene terephthalate (PET).
PET containers are typically manufactured using the well-known stretch blow molding process. This involves the use of a pre-molded PET preform having a threaded portion and a closed distal end. The preform is first heated and then is longitudinally stretched and subsequently inflated within a mold cavity so that it assumes the desired final shape of the container. As the preform is inflated, it elongates and stretches, taking on the shape of the mold cavity. The polymer solidifies upon contacting the cooler surface of the mold, and the finished hollow container is subsequently ejected from the mold.
Another conventional process for fabricating plastic containers is the extrusion blow molding process, in which a continuously extruded hot plastic tube or parison is captured within a mold and inflated against the inner surfaces of the mold to form a container blank. The mold is typically designed to travel at the speed at which the extruded parison is moving when it closes on the parison so that the process can operate on a continuous basis. There are several different types of extrusion blow molding machines, including shuttle molds that are designed to travel in a linear motion and extrusion blow molding wheels that travel in a rotary or circular motion.
The extrusion blow molding process is typically used to form containers that are fabricated from material such as polyolefin or polyethylene. It is not conventionally used for fabricating materials out of PET, although an extrudable PET material has recently been made commercially available.
The stretch blow molding process is the industry standard for forming PET containers that are used to package consumer beverages as well as other materials. However, it has some inherent limitations. These include unsightly gate wells or discontinuities on the bottom portions of containers, and limitations on the possible spectrum of designs that can be realized using the stretch blow molding process.
A need exists for an improved PET plastic container that obviates some of the disadvantages that are inherent to containers that are fabricated using the stretch blow molding process.